The invention relates generally to the field of apparatus and methods used for removing material from inside a conduit. More particularly, the present invention relates to a system capable of loosening and removing material built-up on the inside surface of, or disposed within, a metal conduit.
Undesirable materials that build-up on the inside walls of conduits, such as well tubing, injection lines, pipelines, flowlines, boiler tubes, heat exchangers and water lines, or that otherwise collect inside the conduits, are known to restrict or interfere with the desired movement of fluids, materials and devices, tools, liquids and gases through the conduits. As a result, in many cases, the conduit becomes useless, or inoperable for its intended purpose. For example, thousands of petroleum wells in this country have been shut down or abandoned due to the crippling effect on operations of obstructions in the well tubing. Examples of such undesirable, or obstructive, materials include barium sulfate, strontium sulfate, calcium sulfate, calcium carbonate, iron sulfide, other scale precipitates (such as silicates, sulfates, sulfides, fluorides, carbonates), cement, corrosion products, deteriorated conduit lining, and dehydrated material (such as drilling fluid).
Existing methods of removing obstructive materials from conduits have numerous disadvantages. Various techniques involve the use of a mill or bit to remove obstructive material from conduits. In many applications, the mills or bits have a short useful life due to damage from contact between the mills and bits and commonly occurring hard, dense obstructive materials. The mills or bits must therefore be frequently removed from the conduit and replaced, consuming time and expense. Further, rotation of the mill or bit requires additional component parts, such as a motor, bearings and rotary seals, which are complex and costly to manufacture and operate and subject to failure. Rotary seals typically limit the use or effectiveness of the system due to their vulnerability to wear or damage from high temperatures.
These techniques are also largely ineffective at loosening and removing substantially all obstructive material without damaging the conduit. For example, the inside walls of conduits cleaned with mills or bits are highly subject to damage from contact by the mill or bit. Such contact commonly occurs when the obstructions in the conduit are unevenly dispersed, causing the mill or bit to jam or rub against, or drill into, the side of the conduit. Further, reactive torque due to the rotation of the drill or mill can also cause it to contact the inside surface of the conduit and cause damage thereto. Such reactive torque also accelerates deterioration to the tubing, such as coiled tubing, that carries the mill or bit.
Other conventional cleaning methods utilize jet nozzles that eject only liquid or angular-shaped solid particles in a foam or liquid transport medium. Typical liquid-only systems insertable in a conduit of significant length, such as petroleum tubing and pipelines, operate in low to moderate pressure ranges. These systems have proven ineffective at loosening or removing commonly encountered hard, tightly bonded obstructive materials, such as barium sulfate. The jet systems using angular-shaped solids typically damage the inside surface of metal conduits as a result of the angular solids cutting, scarring and eroding the metal. These systems lack the ability to minimize or control the amount of damage that occurs to the metal conduit; therefore, their use is not entirely satisfactory for many applications. Further, the angular solids provide an erratic erosion pattern, limiting their effectiveness in loosening and removing obstructions.
Thus, there remains a need for a system for loosening and removing undesirable materials built-up on the inside surface of metal conduits, or that otherwise collect inside the conduits, that does not cause substantial or undesirable damage to the conduit. Preferably, the system will be simple, and cost effective and easy to manufacture and operate. Ideally, the system could utilize existing equipment. Especially well received would be a system that can quickly remove all, or substantially all, of the undesirable materials. Ideally, the system would not need to be rotated and would have static seals unaffected by high temperatures. Further, it would be beneficial for the system to be capable of recirculating or reusing its cleaning mixture or the constituents of the cleaning mixture.